Three security personnel were killed and two seriously injured when insurgents ambushed an Assam Rifles patrol in Manipur's Thoubal district on Sunday, official sources said.

Insurgents exploded a powerful bomb when the patrol party belonging to the 34th battalion of the Assam Rifles waspassing through Waithou area on NH 39, 18 km from Imphal, they said.

After exploding the bomb, the insurgents who were hiding beside a roadside hill, sprayed bullets on the securitypersonnel killing three Assam Rifles men on the spot and injuring two others.

It is not immediately known whether there were any casualties on the side of the insurgents, they said.

The injured security men were rushed to the army hospital at Leimakhong area, 25 km from Imphal, the sources said.

Additional security forces have been rushed to the spot and a combing operation is underway to nab the insurgents whohad escaped after the attack. The identity of the insurgents was not immediately known.

The United National Liberation Front, People's Liberation Army, People's Revolutionary Party of Kangleipak were active in the area, the sources said.